How to check if a function is already defined?

Question

How to check if a function is already defined ?

Answer 1

function test(){}

if(typeof test  != "undefined")
    // function is allready defined

Answer 2

typeof return string,so you can use the JavaScript typeof operator to find the type of a JavaScript variable.

if ( typeof(youerFunctionName) === 'undefined' )
{
    console.log('undefined');
}

Answer 3

Like so:

if (typeof myFunc != 'undefined') {
    // Assign myFunc
}

Don't just test it against undefined, which is not a constant and can be reassigned.

Answer 4

Say your function is called func:

if (func) {
  // Function is already defined (or at least something is defined there)
} else {
  // Function is not defined
}